Hot Rod explains why race-car drivers love methanol

Methanol has been a preferred fuel for race-car drivers and teams for decades, for various reasons.

In the movie PUMP, racing teams explain that the lower cost, compared with gasoline, is a big selling point. The footage, which depicts the 91st running of the Race to the Clouds on Pikes Peak, in Colorado, in 2013, includes an interview with one mechanic who says his crew has been running on methanol for 19 years. “It’s just a much better fuel for racing,” he says.

We could go on about the safety of methanol — it burns cleaner than gasoline, is less flammable and burns “cooler” — but come on. What really gets the gearheads salivating is the pure power of methanol.

Methanol has less energy content than regular gasoline, so vehicles get about half the mpg out of the fuel. But it has a higher octane.

As the smart people at Hot Rod magazine explain, race-car engines are built to squeeze more power out of that less-energy-dense methanol, by adjusting the air-to-fuel ratio.

While it’s true that gasoline has a higher energy density (about 18,400 BTU/pound) than methanol (9,500 BTU/pound), if you can burn three times more methanol than gasoline per power stroke, you can make more power. An engine that flows 1,000 cfm of air (about 70 pounds worth) means that on gasoline, the engine will consume about 5.6 pounds of fuel based upon its 12.5:1 max power ratio, giving a total energy output of (5.6 pounds x 18,400 BTU) or 103,040 BTUs of energy. If we do the same calculation on methanol, we get 17.5 pounds of fuel burned, and (17.5 pounds x 9,500 BTU) or 166,250 BTUs of energy—that’s a 60 percent greater energy output.

These folks have forgotten more about engines than most people will ever know, so here’s some more knowledge: Methanol is the better fuel at conserving heat inside an engine. With gasoline, more of that heat is wasted.

Gasoline, when it undergoes a phase change can suck out about 150 BTUs of heat energy per pound of fuel, which results in a temperature drop. Methanol, on the other hand, takes 506 BTUs per pound of fuel of heat energy to make the phase change. When we look at our above example of an engine flowing 1,000 cfm of air, the 5.6 pounds of gasoline will take about 840 BTUs of energy, versus 8,855 BTUs for methanol—more than 10 times as much. This is what makes methanol such an effective fuel in forced-induction applications like turbocharging and supercharging, and it absorbs so much heat that an intercooler often isn’t even needed.

0 replies

Leave a Reply

Want to join the discussion?
Feel free to contribute!

Leave a Reply

Your email address will not be published. Required fields are marked *

*